Multiple version upgrade failed. How to fix?

Okay, so totally my fault, did not read docs beforehand to find that multiple version upgrade is not supported.

Had 15.0.2 installed; and tried to upgrade to 17.

fpm_1  | Initializing nextcloud 17.0.0.9 ...
fpm_1  | Upgrading nextcloud from 15.0.2.0 ...
fpm_1  | Initializing finished
fpm_1  | Nextcloud or one of the apps require upgrade - only a limited number of commands are available
fpm_1  | You may use your browser or the occ upgrade command to do the upgrade
fpm_1  | Set log level to debug
fpm_1  | Turned on maintenance mode
fpm_1  | Exception: Updates between multiple major versions and downgrades are unsupported.
fpm_1  | Update failed
fpm_1  | Maintenance mode is kept active

Then tried to set it to v16, but that fails to start:

fpm_1  | Can't start Nextcloud because the version of the data (17.0.0.9) is higher than the docker image version (15.0.2.0) and downgrading is not supported. Are you sure you have pulled the newest image version?

Same issue happens if I try to go back to previous version that was used (15). Config file lists version 15 as the current one.

What steps should I take to take care of this issue?

just a quick question: you don’t have any backups that you could restore?

Stored data seems to be present (on hdd), and I only have backups of that.

I don’t have any additional backups for Nextcloud configuration; only daily database dumps which would be shame to restore into (not even sure if that version got saved into DB?)

I have found a file called version.php, maybe changing version back to 15 there would help? Don’t want to experiment and mess things even more

Edit: seems that setting version.php to previous version, bumping container to +1 version and then running upgrade/migrations/turning off maintenance is enough to get things working again.